Over the past century the demand for energy has grown exponentially following technological advances. With the growing demand for energy, many different energy sources have been explored and developed. One of the primary sources of energy has been, and continues to be, the combustion of hydrocarbons. However, the combustion of hydrocarbons is usually incomplete combustion that releases both non-combustibles that contribute to smog and other pollutants in varying amounts.
As a result of the pollutants created by the combustion of hydrocarbons, the desire for cleaner energy sources has increased in more recent years. With the increased interest in cleaner energy, alternative energy sources, such as fuel cells, have become more popular and more sophisticated. Research and development of these alternative energy sources has continued to the point that many speculate they will soon compete with the gas turbine for generating large amounts of electricity for cities, the internal combustion engine for powering automobiles, and batteries that run a variety of large and small electronic devices.
In many cases these alternative energy sources operate by conducting an electrochemical reaction that produces electricity and heat. Some of these alternative energy sources are capable of supplying power on a commercial level. However, commercial level, alternative energy sources frequently require high operating temperatures and are housed in large, stationary power plants. Temperature ranges often reach up to 1000 degrees ° C. in such stationary commercial units.
Due to the high temperatures involved, these energy production units are usually housed within a burn chamber to contain the excessive temperatures generated or required for operation. As used herein and in the appended claims, the term “burn chamber” refers to any containment device or structure used to house the power generating components of an energy source.
One of the main disadvantages of a high temperature system is that high operating temperatures require a specialized, sealed outlet between the burn chamber interior and exterior for transferring the power generated out of the burn chamber. Forming the seal on the outlet to the burn chamber has traditionally involved trying to find heat-resistant materials for the seal and the burn chamber that have very close coefficients of thermal expansion (CTE). This allows the burn chamber and seal to have matched expansion under any given conditions and thereby reduces the stress on the seal that develops during high-temperature operation.
In many cases, it is difficult to match the CTE of the non-conductive seal elements with the CTE of the typically conductive burn chamber. Attempting to obtain nearly identical matching of the CTE's may overly restrict the list of materials available for each application. Where materials with similar CTE's can be found, the materials are frequently excessively expensive or, despite the matching CTE's, may have other undesirable characteristics.
One particularly good example of a high temperature, alternative energy source that used a sealed outlet to a burn chamber is a solid oxide fuel cell (SOFC). The temperature required in the burn chamber of a SOFC typically reaches 600° C. or higher. At such high temperatures there is a need for a specialized outlet to house the power conductor from the fuel cell while concurrently preventing the escape of the reactants within the fuel cell.